BTM, I have not done much research. However I am sure there will be expensive provision somewhere favoured by overseas students and postgrads, plus a friend's son (who was probably not proactive enough) found a bed sit in a building owned by a church which was effectively a hall in that there were 20 or so such bedsits. And indeed there is a bedsit in DDs building.
None of this would be ideal as it would be quite isolating, but I doubt DD or your niece will need a plan B. It is very early days. DS, who did not make any effort as he had the option of living at home, found himself invited by friends to take up a room in an existing flat at about Easter.
But I agree. There is huge social pressure on first years. Expectations of University can be very high, and those that don't fall on their feet can feel very "Billy-no-mates" especially if they had a good and supportive friendship group at school. Particularly so with scientists/mathematicians as you need to keep up and cannot afford to have an extended freshers week.
Tell her that it will be OK, and that she can reasonably assume that if she reaches out to people, there will be others in the same boat for house hunting, and indeed others in the same boat in terms of finding "their people".
Traditionally second year was for losing the friends you made in your first year. And there willl always be some who take their time building friendships. This househunting lark is way too early.